1. Field of the Invention
The present invention relates to a cobalt-nickel-iron alloy thin film having a high saturation flux density and a method of forming the same, and a thin-film magnetic head utilizing such an alloy thin film and a method of manufacturing the same.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as a real recording density of hard disk drives has increased. Such thin-film magnetic heads include composite type thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write (recording) head having an induction type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive element (hereinafter also referred to as xe2x80x9cMR elementxe2x80x9d) for reading.
The write head has a bottom pole layer and a top pole layer each of which has a magnetic pole portion. The magnetic pole portions of the bottom and top pole layers are located on a side of the air bearing surface and opposed to each other. The write head further has a write gap layer provided between the magnetic pole portions of the bottom and top pole layers, and a thin-film coil provided such that at least a part of the coil is insulated from the bottom and top pole layers.
There are demands for improvements of the recording characteristics of such a write head to achieve recording in a higher density. One method of improving the recording characteristics of the write head is to use a material having a high saturation flux density as the material of the bottom and top pole layers.
One known material having a high saturation flux density is a cobalt-nickel-iron alloy. It is well known that a bulk material of a cobalt-nickel-iron alloy provides a high saturation flux density, as shown in xe2x80x9cFERROMMAGNETIZMxe2x80x9d authored by Bozorth and in FIG. 2 of Japanese Patent KOKAI Publication No. Sho 62-256989.
It has been reported that an electro-deposition film of a cobalt-nickel-iron alloy formed using electroplating also provides a high saturation flux density when it has a certain composition, as shown in Japanese Patent KOKAI Publication No. Hei 8-241503 and Japanese Patent No. 2821456.
It is natural to assume that a cobalt-nickel-iron alloy, whether it is formed as a bulk material or an electro-deposition film, will provide the same saturation flux density depending on its composition, as long as the composition is the same. In practice, however, an electro-deposition film of a cobalt-nickel-iron alloy formed using electroplating frequently has variation in its saturation flux density which is attributable to inclusion of impurities such as phosphorus (P), boron (B), and sulfur (S) produced in a eutetic manner from organic compounds included in the plating bath and plating conditions such as the current density, the temperature of the bath, and the pH of the bath.
In order for a magnetic material to be preferably used as magnetic layers of a thin-film magnetic head, it must have a soft magnetic property or, more specifically, a small magnetic coercive force, in addition to a high saturation flux density. A range of compositions of cobalt-nickel-iron alloy thin films having high saturation flux densities and preferable soft magnetic properties is a range in which the compositions have crystal structures that are mixtures of a body-centered cubic (bcc) structure phase and a face-centered cubic (fcc) structure phase, as described in the above-mentioned Japanese patent No. 2821456. However, it is difficult to control crystals in such a range of compositions, which is one of the causes of variation of a saturation flux density.
As described above, improvement of recording characteristics of a thin-film magnetic head can be expected from the use of cobalt-nickel-iron alloy thin films as magnetic pole layers of the thin-film magnetic head. However, in order to produce such thin-film magnetic heads on a mass production basis with stable and preferable recording characteristics, it is necessary to suppress variation of the saturation flux density of the cobalt-nickel-iron alloy thin films used for the magnetic pole layers.
It is a first object of the invention to provide a cobalt-nickel-iron alloy thin film having a preferable soft magnetic property and a stable and high saturation flux density, and to provide a method of forming the same.
It is a second object of the invention to provide a thin-film magnetic head in which cobalt-nickel-iron alloy thin films are used as magnetic layers to achieve preferable recording characteristics stably, and to provide a method of manufacturing the same.
A cobalt-nickel-iron alloy thin film according to the invention is a thin film containing 60 to 75 weight % cobalt (Co), 10 to 20 weight % nickel (Ni) and 10 to 20 weight % iron (Fe), and having a crystal structure that is a mixture of a body-centered cubic structure phase and a face-centered cubic structure phase, in which Ib/If is in the range of 0.3 to 0.7 inclusive where Ib represents the intensity of an X-ray diffracted from a (110)-plane of the body-centered cubic structure and If represents the intensity of an X-ray diffracted from a (111)-plane of the face-centered cubic structure.
According to the cobalt-nickel-iron alloy thin film of the invention, in the above-described composition the value of Ib/If is 0.3 or more and 0.7 or less. As a result, it is possible to achieve a preferable soft magnetic property and a stable and preferable high saturation flux density.
A method of forming a cobalt-nickel-iron alloy thin film of the invention is provided for forming a cobalt-nickel-iron alloy thin film containing 60 to 75 weight % cobalt (Co), 10 to 20 weight % nickel (Ni), and 10 to 20 weight % iron (Fe), and having a crystal structure that is a mixture of a body-centered cubic structure phase and a face-centered cubic structure phase through electroplating, wherein the cobalt-nickel-iron alloy thin film is formed such that Ib/If falls within the range of 0.3 to 0.7 inclusive where Ib represents the intensity of an X-ray diffracted from a (110)-plane of the body-centered cubic structure and If represents the intensity of an X-ray diffracted from a (111)-plane of the face-centered cubic structure.
According to the method of forming a cobalt-nickel-iron alloy thin film of the invention, when the cobalt-nickel-iron alloy thin film having the above-described composition is formed through electroplating, the film is formed such that Ib/If falls within the range of 0.3 to 0.7 inclusive. It is thereby possible to obtain a cobalt-nickel-iron alloy thin film having a preferable soft magnetic property and a stable and high saturation flux density.
In the method of forming a cobalt-nickel-iron alloy thin film of the invention, the pH of the plating bath for forming the cobalt-nickel-iron alloy thin film through electroplating may be adjusted to 3.0 to 4.0 inclusive.
In the method of forming a cobalt-nickel-iron alloy thin film of the invention, the value of Ib/If may be controlled by controlling the pH of the plating bath.
A thin-film magnetic head according to the invention comprises:
a medium facing surface that faces toward a recording medium;
a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer;
a gap layer provided between the magnetic pole portions of the first and second magnetic layers; and
a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers, wherein:
at least either of the first and second magnetic layers includes a part made of a cobalt-nickel-iron alloy thin film; and
the cobalt-nickel-iron alloy thin film contains 60 to 75 weight % cobalt, 10 to 20 weight % nickel, and 10 to 20 weight % iron, and has a crystal structure that is a mixture of a body-centered cubic structure phase and a face-centered cubic structure phase, in which Ib/If is in the range of 0.3 to 0.7 inclusive where Ib represents the intensity of an X-ray diffracted from a (110)-plane of the body-centered cubic structure and If represents the intensity of an X-ray diffracted from a (111)-plane of the face-centered cubic structure.
In the thin-film magnetic head of the invention, at least either of the first and second magnetic layers includes a part made of the cobalt-nickel-iron alloy thin film as described above. It is therefore possible to provide preferable recording characteristics stably.
A method of manufacturing a thin-film magnetic head according to the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the magnetic pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers, wherein at least either of the first and second magnetic layers includes a part made of a cobalt-nickel-iron alloy thin film. The method includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the thin-film coil. At least either of the steps of forming the first magnetic layer and the second magnetic layer includes a step of forming the cobalt-nickel-iron alloy thin film through electroplating, the cobalt-nickel-iron ally thin film containing 60 to 75 weight % cobalt, 10 to 20 weight % nickel, and 10 to 20 weight % iron, and having a crystal structure that is a mixture of a body-centered cubic structure phase and a face-centered cubic structure phase, in which Ib/If is in the range of 0.3 to 0.7 inclusive where Ib represents the intensity of an X-ray diffracted from a (110)-plane of a body-centered cubic structure and If represents the intensity of an X-ray diffracted from a (111)-plane of a face-centered cubic structure.
According to the method of manufacturing a thin-film magnetic head of the invention, since the cobalt-nickel-iron alloy thin film used for at least either of the first and second magnetic layers is formed as described above, it is possible to manufacture a thin-film magnetic head having stable and preferable recording characteristics.
In the method of manufacturing a thin-film magnetic head of the invention, the pH of a plating bath for forming the cobalt-nickel-iron alloy thin film through electroplating may be adjusted to 3.0 to 4.0 inclusive.
In the method of manufacturing a thin-film magnetic head of the invention, the value of Ib/If value may be controlled by controlling the pH of the plating bath.
Other and further objects, features and advantages of the invention will appear fully from the following description.